Geothermal Heat Pumps - Underground Renewable Energy
by Lawson Schaller
Solar and wind seem to get most of the attention in the realm of renewable energies these days. Geothermal (ground source) heat pumps generally get less exposure. They are underground after all, but can be an attractive option for those wanting to cut energy usage.
Independence can be gained from non-renewable energy costs by installing a geothermal heat pump, perhaps total independence when installed in conjunction with a solar or PV system. One advantage of geothermal is that the source temperature remains relatively constant and is always accessible. Solar only works when the sun shines, wind generation only works when the wind blows, and hydro when the water flows.
The geothermal systems I am referring to are for homes, small businesses or other onsite applications. Not to be confused with large scale industrial geothermal plants that operate around the world. For many folks, images of generating plants near geysers may come to mind.
Ground source (geothermal) heat pumps use the constant temperature of the ground for heating and cooling. They move heat from one place to another. Generally speaking the temperature underground stays relatively constant, warmer than the winter air and cooler than the summer air. Pipes, also known as loops, are buried in the ground and circulate water, or refrigerants - fluids with low boiling points that vaporize easily. During cold winters (imagine below-freezing nights) the piped fluids bring warmer temperatures to the home. During hot summers (imagine 100 degree days) the fluids bring cooler temperatures to the home; or, more accurately (without going into details) the heat is extracted, or pumped from the house and dispersed to the earth. Like an air conditioner, the geothermal unit compresses or expands the refrigerant to raise or lower its temperature. The refrigerant then moves into condenser/evaporator coils. This is of course is a simplified, abbreviated explanation and I'm no engineer.
Details of the loop or pipe design vary. For example there are horizontal, vertical and spiral loop systems. Heat pump systems vary and have working parts that move and compress the fluids, transfer and distribute the energy thru the home via radiant floor systems, sometimes radiators and/or via forced air systems. They can also be tied into hot water systems. Figuratively and literally there are moving parts—compressors, soil conditions etc. They all have their pros and cons.
The drilling for the piped closed loop systems may only require a small area. There are open loop systems which we will not go into but they essentially extract and dump water and have their own set of problems. So, with the drilling it is possible to have little impact on existing landscapes. On the other hand there will be digging equipment on site and a much larger area may be disturbed. It will depend on the piped loop design, site access, size of the system, etc. The drilling must be professionally planned and laid out to maximize the system and also to avoid other underground utilities.
In the house: Pumps cycle water through the pipe loop to the heart of the system: the geothermal unit, which acts as furnace and air conditioner. This machine uses refrigerant and the temperate water from the underground pipes to heat or cool air. The air is then circulated through standard ductwork. With a device called a desuperheater, the unit uses excess heat to warm up domestic hot water at no added cost. The results feel the same as those from any standard forced-air HVAC system.
Air in the ducts (1), refrigerant in the geothermal unit (2), and water in pipes (3) flow past each other like interlocking gears. Water brought from underground transfers heat to the refrigerant, or absorbs heat from it, depending on the season. Like an air conditioner, the unit compresses or expands the refrigerant to raise or lower its temperature. Finally, the refrigerant, now heated to 180 F or chilled to 40 F, fills condenser /evaporator coils. Air in the ducts blows across the coils to be cooled or warmed, then flows through the house. Popular Mechanics
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Geothermal heat pumps are more durable and require less maintenance and energy than traditional systems. They are also quieter. I strongly recommend you contact a local expert to determine and assess your options. Solarponics is a local company that has expertise in geothermal heat pumps and other renewable energy systems. Prior to sizing and installing a geothermal heat pump, maximize insulation, weather stripping, and other opportunities to best seal your buildings envelope or structure. Take advantage of site location and passive solar opportunities.
Costs and payback periods can vary. I have read of payback periods being between five and fifteen years. Many things can impact your installation costs and therefore payback periods. Federal tax credits and other incentives from local governments and utilities come into play. Efficiencies of the home and the type of system being replaced as well as the type and cost of energy you used to heat and cool your home impact your payback period. Geothermal units are efficient and can start saving immediately on monthly payments to energy providers.
As suggested earlier, one could install a geothermal heat pump and also install solar panels to augment/supply the power requirements of the heat pump and approach or possibly get to a net zero position - freeing one from the dependence and fluctuating costs of fossil fuels. Now that is pretty exciting!
Great Horned Owl image on banner by Cleve Nash |
